The ability to silylate organic moieties has attracted significant attention in recent years, owing to the utility of the silylated materials in their own rights or as intermediates for other important materials used, for example, in agrichemical, pharmaceutical, and electronic material applications. Further, the ability to functionalize polynuclear aromatic compounds with oganosilanes provides opportunities to take advantage of the interesting properties of these materials.
Historically, the silylation of aromatic compounds has been achieved via free radical processes involving thermally, photochemically, or by otherwise derived radical sources. Aromatic compounds are known react with silicon hydrides in the gas phase at 500-850° C., in the liquid phase under autogeneous pressure at 350-500° C., in the presence of peroxides at 135° C. under gas phase condensations, and using electrical discharge reactions. Such reactions conditions are not amenable to non-volatile or thermally sensitive materials.
At present, the most common approach to heteroaromatic C—Si bond construction involves the interception of heteroaryl lithium or magnesium reagents with silicon electrophiles. However, this method is often limited in scope and requires prefunctionalization of heteroarenes by using pyrophoric organometallic species in stoichiometric quantities. Powerful heteroaromatic functionalization strategies, such as Minisci-type radical substitutions and Friedel—Crafts reactions, have been of limited use for C—Si bond construction owing to the difficulty of generating the corresponding silyl radicals and silylium ions.
More recently, the transition metal mediated aromatic C—H silylation has been described, with different systems described based on, for example, Co, Rh, Ir, Fe, Ru, Os, Ni, Pd, and Pt catalysts. But certain electronic applications, the presence of even low levels of such residual can adversely affect the performance of the silylated materials. Similarly, in certain pharmaceutical or electronic applications, limits on residual transition metals are fairly strict, and the ability to avoid them entirely offers benefits during post-synthesis work-up.
The present invention takes advantage of the discoveries cited herein to avoid at least some of the problems associated with previously known methods.